Study On Degradation Techniques Of PBDEs And Its Possible Mechanism

Polybrominated diphenyl ethers(PBDEs) are brominated flame retardants(BFRs) and a new class of persistent organic pollutants(POPs).They have a strong toxicity, and attracted much attention in recent years. In this thesis,the degradation method and itsdecompostion mechanism of decabromodiphenyl ether(Deca-BDE) have been studied.A novel method for debromination of Deca-BDE by palladium/titanium as catalyst under mild reaction conditions have been developed. The oppitmized reaction conditions have been investigated. Complete debromination of Deca-BDE was achieved at 40℃under 0.5 Mpa hydrogen pressure after 2.5 hour reaction with 1 mg/L palladium/titanium as catalyst. With the aid of the technology of High Performance Liquid Chromatography (HPLC), Gas Chromatography (GC), Gas Chromatography/Mass Spectrumetery (GC/MS) and Ion Chromatorahpy (IC), partial degradation products were analyzed. The possible pathway of reductive debromination of Deca-BDE from high brominatied compound to low brominated compound was suggested,there has a good prospect for industrial application. The good reuse was approved by that.Above 80%of debromination after ten times recycling of the catalysts indicated its good reuse. The catalysis mechanism of palladium was evaluated by determination of valence change of the surface catalysts before and after reaction with X-ray Photoelectron Specturm (XPS). The results showed that the debromination method is high effective and environmental friendly and might have a good prospect for industrial application.Based on previous investigation of the wet oxidation of Deca-BDE, the reaction ration of co-solvent tetrahydrofuran (THF) was optimized to 1%. Under 1%THF,100 mol% of NaNO2,97.8%degradation of Deca-BDE was achieved under 150℃,0.5MPa of oxygen after 2 hours reaction. A simple, fast oxidative method was developed for decomposition of Deca-BDE.A novel silica-based ion exchanger has been developed via polar-copolymerization method. The method allows the capacity of the ion exchanger easy control and alleviates the nonspecific interactions of the residual silanols as well. The achieved ion exchangers demonstates baseline separation for the common inorganic anions and indicates good efficiency, take NO2 as example, its plate number is 80000/m; The dominant separation mechanism of the ion exchanger has been observed to be based on ion exchange; By the column achieved, bromide concentration in the above degradation products has been determined and the anions containing in the saliva and tap water have also been determined.